The present invention relates to an apparatus for scanning a member in a plane perpendicular to its forward movement direction and more especially applied to the scanning of a welding torch in two directions contained in a scanning plane perpendicular to its forward movement direction for filling by means of a welding bead a joint between two parts.
However, the invention is not limited to the scanning of a welding torch, also applying e.g. to the scanning of a non-destructive control sensor, a cutting, machining, milling, gluing or other type of tool or the like.
The scanning movement of a welding torch is necessary for filling angled joints or those having wide chamfers. This scanning movement is carried out in a plane perpendicular to the forward movement of the welding torch along said joint. It is generally used for processes with a good filling power, such as MIG, MAG and lined wire processes.
In conventional apparatuses, the scanning movement is limited to one scanning direction along which the welding torch has an oscillatory movement. This scanning direction contained in the plane perpendicular to the advance of the torch is often parallel to the external bisector of the welding joint.
FIG. 1 is a diagrammatic drawing illustrating the scanning movement of the torch in known apparatuses. The welding torch 2 is placed right in front of a joint 4 defined by the juxtapositioning of two chamfered parts 6, 8. These parts are shown in section in a plane transverse to the direction of the joint. An arrow 10 indicates the movement of the welding torch 2 in this cutting plane.
The curve of position x of the end of the welding torch 2 on the scanning axis X as a function of the time t is also shown, in correspondence with said joint. The movement of the welding torch is totally determined by the amplitude a of its oscillation, the duration of t.sub.e of the time lag at the ends and the scanning speed. These variables, which define the oscillation period T, can be independently adjusted, which makes it possible to optimize the welding, no matter what the configuration of the joint and the welding procedure used. However, this method is not always adequate for completely filling the joint with a welding bead, particularly when the joint is very open.
The object of the invention is to obviate this disadvantage. For filling angle joints and wide chamfers, an attempt is made to produce a bidimensional scanning movement in the plane transverse to the forward movement of the welding torch. In order to follow the profile of the joint in an optimum manner, it is important to be able to independently vary the torch displacement parameters.
In order to achieve this objective, it is possible to utilize a welding torch support system with two crossed carriages, each actuated or operated by a motor. However, the generation of electronic position signals synchronized along the two scanning axes is difficult to realize in a simple manner.